In recent years, the demand for flat-panel display devices such as a liquid crystal display device has rapidly grown because of the thinness, lightness, and energy-efficiency of such devices. Amongst others, an active-matrix display device is adopted in various devices including mobile information devices. The active-matrix display device includes on-state pixels and off-state pixels those are electrically separated and a pixel switch functioning to hold an image signal on the on-state pixel in each pixel.
As such a flat-panel active-matrix display device, an organic electroluminescent (EL) display device using self-luminescent elements is now the focus of keen research and development. The organic EL display device does not require a backlight, and is suitable for both movie playing use because of its rapid response and cold environmental use because of its luminosity which does not decrease even at a low temperature.
As to the electronic devices such as a mobile information device, there has been a great need for reduction of power consumption. An electronic device including a display device is considered, large power is used for driving the display device, and thus, reduction of the power consumption for driving the display device is required.
In general, the power consumption in the display device such as an organic EL element increases when the luminosity of the display screen increases. In order to reduce the power consumption in the display device, a luminosity control circuit is provided therewith.